1. Field of the Invention
This invention relates broadly to methods and devices for treating articles in a gaseous atmosphere. In a preferred embodiment, the invention relates to methods and devices for plasma treating ophthalmic lenses, especially contact lenses, to increase hydrophilicity.
2. Description of the Related Art
Various treatments of articles in a gaseous atmosphere are known. For example, the treatment of articles in a plasma (i.e., ionized gas) atmosphere has been used to produce surface coatings or modify the surface of an article, so that the surface properties differ from the properties of the native material. Plasma surface treatments are especially useful in the production of ophthalmic lenses, such as contact lenses.
For example, U.S. Pat. No. 4,312,575, issued to Peyman, et al., on Jan. 26, 1982, discloses the treatment of the surfaces of soft contact lenses in an electrical glow discharge polymerization process. The atmosphere consists essentially of hydrocarbons, halogenated hydrocarbons, halogenated hydrocarbons and hydrogen, hydrocarbons and an elemental halogen, and mixtures thereof. The lenses are supported in a ring structure having an arcuate slot in which the lens periphery rests. A second coating step is required in order to coat the lens periphery, because a peripheral portion of the lens is blocked by the support structure.
U.S. Pat. No. 4,632,844, issued to Yanagihar, et al., on Dec. 30, 1986, discloses an optical product having a thin surface film obtained by subjecting a mixed gas of oxygen and an alkene to plasma polymerization in the presence of the optical product. The optical product is supported on a supporting table placed inside the reaction vessel, and the exposed surface of the optical product is treated. Again, in this configuration, one half of the lens is treated and the other half is sheltered ("shadowed") from the reactive plasma.
While there have been numerous attempts at improving plasma surface treating processes, there remain problems with treatment uniformity and processing efficiency.